Polymer blend



United States Patent 3,444,117 POLYMER BLEND John J. Higgins and Nova E. Stucker, Westfield, N.J., as-

signors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Apr. 6, 1966, Ser. No. 540,533 Int. Cl. C08f 29/06 U.S. Cl. 260-285 9 Claims ABSTRACT OF THE DISCLOSURE A blend of atactic polypropylene, low molecular weight polybutene and an isobutylene polymer provides an improved polymer blend which may be used in such applications as wax blend formulations, hot melt adhesives, and asphalt compositions.

This invent-ion relates to a novel elastomeric material serving as a base for the production of adhesives, mastics and sealants. More specifically, it relates to a blend of atactic polypropylene, low molecular weight polybutene and an isobutylene polymer, which blend is a valuable intermediate for the formation of adhesives, sealants, and the like.

-It is known in the art to use butyl rubber in sealant and adhesive applications because, of the rubbers flexibility, good tack, and outstanding aging and weathering resistance. However, butyl rubber cannot easily be blended with other materials because of its inherent toughness, and therefore it is necessary to use expensive, sophisticated, high shear mixing equipment to break down the tough polymer bales. Additionally, very large amounts of solvents must be used to plasticize butyl mastics and caulks. Subsequently, the solvent evaporation leads to excessive shrinkage of the caulking or mastic materials. It has now been found that these problems may be avoided if there is substituted for the butyl a blend of an atactic polypropylene, low molecular Weight bolybutene, and an isobutylene polymer. This blend has superior physical properties, is easily processed in the absence of solvent and is highly extendible.

The blend of the present invention is produced by mixing together about 10-40 weight percent, preferably about 25% of a substantially atactic polypropylene, with -80 weight percent, preferably about 50 weight percent, of a low molecular weight polybutene, and 10-40 weight percent, preferably about weight percent, of an isobutylene polymer. The blended material comprises a composition which has many uses. For example, it may be mixed with an organic solvent, such as toluene and used as a pressure-sensitive adhesive. It may also be used with wax or paraffin as a hot melt adhesive. It may further be used to produce caulking compounds and rubberized asphalts. 1

The polypropylene which is used for the invention is a substantially atactic (i.e. amorphous) polymer. This polymer is produced, "for" example, under' low pressure conditions with the aid of a Ziegler-type polymerization catalyst. The amorphous polypropylene should have a viscosity of between about 1000-50000 centipoises (190 C. Brookfield). The polypropylene may contain a small amount of crystallinity, i.e., suitably less than 10%, but it is preferred that it contain substantially no crystal'linity.

The polybutene which is useful in this invention, is a low molecular Weighf'polymerof butene which has a consistency varying from liquid to semi-solid. The molecular weight of the polybutene should be in the range of about 300-3000 (as determined by Mecrolab Osmometer) The isobutylene polymer which is useful in this invention, is either Yistanex, a homopolymer of isobutyl- 3,444,117 Patented May 13, 1969 ene; or an isobutylene based butyl rubber. Butyl rubber is prepared by copolymerizing isobutylene with a minor amount of a C to C diolefin such as isoprene or butadiene. The preparation of butyl rubber, and its composition, is described in Patent No. 2,356,128 issued to Sparks and Thomas. The molecular weight of the isobutylene polymer is not critical to this invention, although -it is preferred that the polymer have a Staudinger molecular weight of between about 30,000 and 200,000.

The blend of this invention may be solvated with bydrocarbon or chlorinated hydrocarbon diluents of a very wide variety. Illustrative of these are hexane, toluene, benzene, cyclohexane, chlorobenzene, xylene, and mineral spirits. Solvents containing oxygen, such as acetone or isopropyl alcohol are not useful. In the production of pressure-sensitive adhesives, about 20 to '80 volume percent of solvent is used based on the total volume of polymer blend.

The blends of this invention may also be used in wax blend formulations for use as hot melt adhesives and coatings. Thus, they may be blended in any proportion with parafiin or microcrystalline wax for such purposes. The elastomer blend-wax formulation is highly compatible and has a low viscosity which minimizes processing difiicnlties. Additionally, it has superior properties as an adhesive or a coating.

The blends of this invention can also be mixed with any proportion of asphalt to produce rubberized a-sphalts having superior low temperature ductility and excellent impact strength. Asphalt containing 2 to 20% of the blends are of greatest economic interest.

Excellent caulking compounds may be produced by mixing the blends of this invention with conventional proportions of tackifying resins such as steam cracked petroleum resins, or hydrogenated rosins; and fillers such as whitings and clays.

EXAMPLE 1 The blend of this invention was prepared by mixing the following polymers in a kneader:

Materia-lz. v I Parts by weight Atactic polypropylene =(no crystallinity; number average molecular weight -3000) 1 Bu-tyl rubber (copolymer o f about 98.5 weight percent isobutylene and about 1.5 Weight percent isopre'ne; Staudinger molecular weight about 44,000) 1 :Polybutene \(molecular weight about 890 by Mecrolab Osmometer) ;"2

After kneading for 180 minutes with slow addition of the polybutene, a tough, tacky, viscous material was formed with the following properties:

Specific gravity 0.90. Volatiles at C., percent by Weight 0.30. Ash content, percent by Weight 0.50. Color Amber. Solubility Miscible with hydro carbon or chlorinated hydrocarbon solvents.

3,444,117 3 4 EXAMPLE 2 standpoint, neither the softening point nor viscosity in- Formulations of the polymer blend with waxes are crease was excessive. Dther tests have indicated that the useful to produce hot melt adhesives and coatings. blends of this mvlmtlon greatly Increase flexural wax blends were made using the polymer blend f strength of conventional, pourable, asphalt mixes. Example 1 and two typical waxes, a paraffin (Essowax 5 EXAMPLE 4 #5010, a 151 F. melting point distilled paraifin) and a microcrystalline wax (Mikrovan 1750, petrolatum melting point 175 F.). The solutions were prepared in a Valuable caulking compounds can be made with the blends of this invention. A typical formulation is shown Beken mixer steam heated to 200 F. Samples of each below blend were allowed to cool and were then placed in Material: Parts by weight ovens at three test temperatures (212 F., 250 F., and Polymer blend of Example 1 200 300 F.) without agitation. These samples were examined Piccopale 100 1 at 16 and 64 hours. Button 100 2 50 The compatibility was excellent since the blends showed Hercolyn 3 8.5 no signs of separation or decomposition. The solutions 15 Denatured alcohol 1.3 were clear of haze, and stirring by hand did not reveal Bentonite 4 25 a second layer of material. The predominant odor was Atomite whiting 400 that of the base wax and no change in odor or color was Talc 100 noticed even when stored at 300 F. The viscosity of Butile TiO 50 the blends increased in a regular mannFr wifl 1 in- Petroleum resin having 100 F. melting point. creasing polymer content. For an elastomeric additive, Low Molecular weight butadiene-styrene copolymer. the increase in viscosity was very slight and this property 13 2 5? g ggl rosin having Viscosity constitutes a major processing advantage for this inter- Bentonite clay. mediate product. 'Powdered calcium carbonate.

Large concentrations of additive can be used with only e formu n wa miXed r y in a header; I10 minor changes in the flow and handling properties of the mills or high shear mixing equipment were required. base wax. The good compatibility and low viscosity also Shrinkage was held to a minimum since it was not necesreduced the necessary blending time. Starting with the sary to incorporate large amounts of solvent. Excellent wax and the intermediate (i.e., the polymer blend of adhesion of the resulting caulk to a variety of building Example 1) at room temperature in a one-gallon Beken 30 substrates was obtained. mixer, the molten wax-polymer blend was visually This invention has been described in connection with homogeneous within 30 minutes, and was dumped within certain specific embodiments thereof; however, it is to minutes. be understood that these are by way of example and not TABLE I.-WAX BLENDS In paratfin at- In microwax at- Compatibility Good, all solutions haze tree, clear Viscosity (cps at 250 F 7 30 8, 600 22 75 20, 000 Odor 300 None None V. slight None None V. slight Color Lt. yellow Lt. earmel Lt. yellow Lt. carmel Blending time--- Fast and easy to blend EXAMPLE 3 by way of limitation, and it is not intended that the in- Another hot melt application where rubber based addi- 45 g i i i ffq f tives have proven effective is in asphalt based adhesives 1 Z c b1 d f b 10 40 and sealers. Rubberized asphalts generally have better composltlon compnslng 0 3 out low temperature ductility, better impact strength and betg of i i i i polyprollj'ylellle weig percen 0 p0 y u ene aving a mo ecu ar ter temperature susceptibility than the r nonmodified 50 Weight in the range of about 30041000 and IMO weight counterparts. The blend of this invention imparts the adpercent of an isobutylene Polymer having a molecular vantages of rubber to asphalt but is much easier to incorweight of between about 30,000 and 200,000, Selected P AS shown In Table Wlth a Standard Propeller from the class consisting of polyisobutylene and an isotype mixer, five minutes at 300 F. was sufiicient to blend butylene based butyl rubber.

in the Product of EXamPle While one hour at 3500 2. The composition of claim 1 wherein the isobutylene was necessary for another proprietary rubber compound polymer is polyisobutylene Sold r this Prolongfid eXPQSUYB t0 emp ra- 3. The composition of claim 1 wherein the isobutylene tures can severely degrade the asphalt, thus the ease with polymer i b l bb a copolymer of isobutylgng ith which the blend of this invention can be processed avoids a minor amount of a C to C diolefin.

such degradation. 4. The composition of claim 1 containing about 25 TABLE II.-MODIFIED ASPHAL'IS l u Additive Penetra- Soitenlty at ity at Penetra- Blendlug content tion at ing point, 39.2 F. 275 F. tion Additive required (percent) 77 F. F. (0111.) SFS Index 3 Blend of Example 1 5 min. at 300 F--... 5 86 120 9. 5 283 -0. 1 10 79 131 11 738 +1. 2

Commercial elastomeric additive One hour at 350 F.. 5 53 127 7. 5 403 -0. 3 66 132 7 718 +0. 4

1 -100 Penetration asphalt.

I Penetration Index is a measure 0! the temperature susceptibility of a binder and depends on the softening point and penetration relative to one another. The higher the penetration index the better the temperature susceptibility.

I Ramfiex V-17; a special process reclaim rubber in a black, free flowing, asphalt soluble form. Density is 1.14 to 1.16, bulk density 14-16 lbs/ L particle size is through 10 mesh and 80% through 20 mesh screen.

These data show that blending was very easily accomweight percent of polypropylene, 50 weight percent of plished and that low temperature ductility and temperapolybutene and 25 weight percent of the isobutylene ture susceptibility were improved. From an application polymer.

5. The composition of claim 4 wherein the isobutylene polymer is butyl rubber, a copolymer of isobutylene with a minor amount of a C to C diolefin.

6. The composition of claim 5 which is blended with asphalt.

7. The composition of claim 5 which is blended with wax.

8. The composition of claim 5 to which has been added a hydrocarbon or chlorinated hydrocarbon solvent.

9. The composition of claim 5 which is blended with a tackifying resin and filler to produce a caulking compound.

References Cited UNITED STATES PATENTS 2,131,342 9/ 1938 Baldeschwieler. 2,202,3 63 5/ 1940 Wiezevich. 2,572,458 10/1951 Eustis.

Sayko.

Schramm.

Kirk et a1.

Ridenour.

Sterling.

Belak et a1.

Cox.

Edwards et a1. 260889 FOREIGN PATENTS Great Britain.

MORRIS LIEBMAN, Primary Examiner.

JOHN E. TERMINI, Assistant Examiner.

US. Cl. X.R. 

